The invention relates to chemotherapy and drug resistance.
Cancer chemotherapy commonly involves the administration of one or more cytotoxic or cytostatic drugs to a patient. The goal of chemotherapy is to eradicate a substantially clonal population (tumor) of transformed cells from the body of the individual, or to suppress or to attenuate growth of the tumor. Tumors may occur in solid or liquid form, the latter comprising a cell suspension in blood or other body fluid. A secondary goal of chemotherapy is stabilization (clinical management) of the afflicted individual""s health status. Although the tumor may initially respond to chemotherapy, in many instances the initial chemotherapeutic treatment regimen becomes less effective or ceases to impede tumor growth. The selection pressure induced by chemotherapy promotes the development of phenotypic changes that allow tumor cells to resist the cytotoxic effects of a chemotherapeutic drug.
The present invention concerns DR6, a gene which is expressed at a relatively high level in a number of drug resistant cancer cell lines. DR6 nucleic acids and polypeptides are useful in, for example, diagnostic methods related to identification of drug resistant cells (e.g., cancer cells). DR6 nucleic acids and polypeptides are also useful in screening methods directed to the identification of compounds that can modulated (increase or decrease) the drug resistance of a particular cell type or multiple cell types.
The DR6 1792 nucleotide cDNA described below (SEQ ID NO:1) has a 1263 open reading frame (nucleotides 96 to 1358 of SEQ ID NO:1; SEQ ID NO:3) which encodes a 421 amino acid protein (SEQ ID NO:2).
The invention features a nucleic acid molecule which is at least 45% (or 55%, 65%, 75%, 85%, 95%, or 98%) identical to the nucleotide sequence shown in SEQ ID NO:1, SEQ ID NO:3, the nucleotide sequence of the cDNA insert of the plasmid deposited with ATCC as Accession Number (the xe2x80x9ccDNA of ATCC PTA-1881xe2x80x9d), or a complement thereof.
The invention features a nucleic acid molecule which includes a fragment of at least 15 (20, 25, 30, 150, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 800, 900, 1000, 1100, 1200 or 1266) nucleotides of the nucleotide sequence shown in SEQ ID NO:1, SEQ ID NO:3, the nucleotide sequence of the cDNA ATCC PTA-1881, or a complement thereof.
The invention features a nucleic acid molecule which includes a nucleotide sequence encoding a protein having an amino acid sequence that is at least 80% (or 82%, 85%, 95%, or 98%) identical to the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA of ATCC PTA-1881.
In an embodiment, a DR6 nucleic acid molecule has the nucleotide sequence shown in SEQ ID NO:1, SEQ ID NO:3, or the nucleotide sequence of the cDNA of ATCC PTA-1881, or a complement thereof.
Also within the invention is a nucleic acid molecule which encodes a fragment of a polypeptide having the amino acid sequence of SEQ ID NO:2, the fragment including at least 15 (25, 30, 50, 100, 150, 200, 300, 400 or 421) contiguous amino acids of SEQ ID NO:2 or the polypeptide encoded by the cDNA of ATCC Accession Number PTA-1881.
The invention includes a nucleic acid molecule which encodes a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or the amino acid sequence encoded by the cDNA of ATCC Accession Number PTA-1881, wherein the nucleic acid molecule hybridizes to a nucleic acid molecule comprising SEQ ID NO:1 or SEQ ID NO:3 under highly (or moderately) stringent conditions.
In general, an allelic variant of a gene will be readily identifiable as mapping to the same chromosomal location as the gene. For example, in Example 1, the chromosomal location of the human DR6 is shown to be chromosome 19, position 41-43 cM, near marker stSG4364. Thus, allelic variants of human DR6 will be readily identifiable as mapping to the human DR6 locus on chromosome 19 near genetic marker stSG4364.
Also within the invention is an isolated DR6 protein having an amino acid sequence that is at least about 80% (82%, 85%, 95%, or 98%) identical to the amino acid sequence of SEQ ID NO:2. The amino acid sequence of such DR6 proteins can include one or more (e.g., 2, 5, 10, 15, 30, 25, 30 or more) conservative amino acid substitutions. For example, 1%, 2%, 3%, 5%, 7%, 10%, or 15% of the amino acid residues can be replaced by conservative substitution.
Also within the invention is an isolated DR6 protein which is encoded by a nucleic acid molecule having a nucleotide sequence that is at least about 65%, preferably 75%, 85%, or 95% identical to SEQ ID NO:3 or the protein coding portion of the cDNA of ATCC PTA-1881.
Also within the invention is a polypeptide which is a naturally occurring allelic variant of a polypeptide that includes the amino acid sequence of SEQ ID NO:2 or an amino acid sequence encoded by the cDNA insert of the plasmid deposited with ATCC as Accession Number PTA-1881, wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a nucleic acid molecule comprising SEQ ID NO:1 or SEQ ID NO:3 under highly (or moderately) stringent conditions.
Another embodiment of the invention features DR6 nucleic acid molecules which specifically detect DR6 nucleic acid molecules. For example, in one embodiment, a DR6 nucleic acid molecule hybridizes under stringent conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:1, SEQ ID NO:3, or the cDNA of ATCC PTA-1881, or a complement thereof. In another embodiment, the nucleic acid molecule is at least 15 (20, 25, 30, 150, 100, 150, 200, 250 300, 350, 400, 450, 500, 550, 600, 650, 700, 800, 900, 1000, 1100, 1200 or 1266) nucleotides in length and hybridizes under stringent conditions to a nucleic acid molecule comprising the nucleotide sequence shown in SEQ ID NO:1, SEQ ID NO:3, the cDNA of ATCC PTA-1881, or a complement thereof. In yet another embodiment, the invention provides an isolated nucleic acid molecule which is antisense to the coding strand of a DR6 nucleic acid.
Another aspect of the invention provides a vector, e.g., a recombinant expression vector, comprising a DR6 nucleic acid molecule of the invention. In another embodiment the invention provides a host cell containing such a vector or an isolated DR6 nucleic acid molecule. The invention also provides a method for producing DR6 protein by culturing, in a suitable medium, a host cell of the invention containing an isolated nucleic acid molecule or recombinant expression vector such that a DR6 protein is produced.
Another aspect of this invention features isolated or recombinant DR6 proteins and polypeptides. Preferred DR6 proteins and polypeptides possess at least one biological activity possessed by naturally occurring human DR6 protein, e.g., (1) the ability to form protein:protein interactions with membrane proteins; (2) the ability to form protein-protein interactions with a clatherin; (3) the ability to bind a DR6 ligand; (4) and the ability to increase drug resistance.
The DR6 proteins of the present invention, or biologically active portions thereof, can be operatively linked to a non-DR6 polypeptide (e.g., heterologous amino acid sequences) to form a DR6 fusion protein. The invention further features antibodies that specifically bind DR6 proteins, such as monoclonal or polyclonal antibodies. In addition, DR6 proteins or biologically active portions thereof can be incorporated into pharmaceutical compositions, which optionally include pharmaceutically acceptable carriers.
In another aspect, the present invention provides a method for detecting the presence of DR6 activity or expression in a biological sample by contacting the biological sample with an agent capable of detecting an indicator of DR6 activity such that the presence of DR6 activity is detected in the biological sample. For example, the invention includes a method for detecting the presence of a DR6 polypeptide in a sample. This method features the steps of contacting the sample with a compound which selectively binds to the polypeptide and then determining whether the compound binds to a polypeptide in the sample.
In some cases, the compound which binds to the polypeptide is an antibody. The invention also features methods for detecting the presence of a DR6 nucleic acid molecule in a sample. This method includes the steps of contacting the sample with a nucleic acid probe or primer which selectively hybridizes to a DR6 nucleic acid molecule (e.g., an mRNA encoding DR6); and then determining whether the nucleic acid probe or primer binds to a nucleic acid molecule in the sample.
In another aspect, the invention provides a method for modulating DR6 activity comprising contacting a cell with an agent that modulates (inhibits or stimulates) DR6 activity or expression such that DR6 activity or expression in the cell is modulated. In one embodiment, the agent is an antibody that specifically binds to DR6 protein. In another embodiment, the agent modulates expression of DR6 by modulating transcription of a DR6 gene, splicing of a DR6 mRNA, or translation of a DR6 mRNA. In yet another embodiment, the agent is a nucleic acid molecule having a nucleotide sequence that is antisense to the coding strand of the DR6 mRNA or the DR6 gene.
In one embodiment, the methods of the present invention are used to treat a subject having a disorder characterized by aberrant DR6 protein or nucleic acid expression or activity by administering an agent which is a DR6 modulator to the subject. In one embodiment, the DR6 modulator is a DR6 protein. In another embodiment the DR6 modulator is a DR6 nucleic acid molecule. In other embodiments, the DR6 modulator is a peptide, peptidomimetic, or other small molecule.
The present invention also provides a diagnostic assay for identifying the presence or absence of a genetic lesion or mutation characterized by at least one of: (i) aberrant modification or mutation of a gene encoding a DR6 protein; (ii) mis-regulation of a gene encoding a DR6 protein; (iii) aberrant RNA splicing; and (iv) aberrant post-translational modification of a DR6 protein, wherein a wild-type form of the gene encodes a protein with a DR6 activity.
The invention also features methods for identifying a compound which modulates the expression of DR6. In general, such methods entail measuring the expression of DR6 in the presence and absence of a teat compound and identifying those compounds which alter the expression of DR6.
Also within the invention are kits that include a compound which selectively binds to a DR6 polypeptide or nucleic acid and instructions for use. Such kits can be used to determine whether a particular cell type or cells within a biological sample, e.g., a sample of patient cells, are drug resistant.
The invention features methods for identifying a compound which binds to a DR6 polypeptide. These methods include the steps of contacting a DR6 polypeptide with a test compound and then determining whether the polypeptide binds to the test compound. In various embodiments of these methods, the binding of the test compound to the DR6 polypeptide is detected using an assay which measures binding of the test compound to the polypeptide or using a competition binding assay.
The invention also includes a method for modulating the activity of a DR6 polypeptide. This method includes the steps of contacting the polypeptide or a cell expressing the polypeptide with a compound which binds to the polypeptide in a sufficient concentration to modulate the activity of the polypeptide.
In another aspect, the invention provides a method for identifying a compound that modulates the activity of a DR6 polypeptide (e.g., a DR6 protein). In general, such methods entail measuring a biological activity of the polypeptide in the presence and absence of a test compound and identifying those compounds which alter the activity of the polypeptide. One such method includes the steps of contacting the polypeptide with a test compound and then determining the effect of the test compound on the activity of the polypeptide to thereby identify a compound which modulates the activity of the polypeptide.
Other aspects of the invention are methods and compositions relating to drug resistance. A xe2x80x9cdrug-resistant henotypexe2x80x9d refers to a cellular phenotype which is associated with increased survival after exposure to a articular dose of a drug, e.g., a chemotherapeutic drug, compared to a cell that does not have this phenotype. A xe2x80x9cdrug-resistant cellxe2x80x9d refers to a cell that exhibits this henotype. Drug resistance commonly occurs at multi-drug resistance (multiple drug resistance) in which a cell population or tumor becomes relatively resistance to a drug to which it has been exposed as well as to other drugs to which it has not been exposed.
Drug resistance can be characterized by lower intracellular concentration of a drug compared to a non-resistant cell or a less resistant cell as well as altered ability of a drug to affect its target compared to a non-resistant cell or a less resistant cell. Drug resistance is described in detail by Hochhauser and Harris ((1991) Brit. Med. Bull. 47:178-96); Simon and Schindler ((1994) Proc. Nat""l Acad Sci USA 91: 3497-504); and Harris and Hochhauser ((1992) Acta Oncologica 31:205-213); Scotto et.al. ((1986) Science 232: 751-55). Multi-drug resistance can be associated with, for example, altered composition of plasma membrane phospholipids; increased drug binding and intracellular accumulation; altered expression or activity of plasma membrane or endomembrane channels, transporters or translocators; altered rates of endocytosis and associated alteration in targeting of endosomes; altered exocytosis; altered intracellular ionic environments; altered expression or activity of proteins involved in drug detoxification; and altered expression or activity of proteins involved in DNA repair or replication.
Also within the invention is a method of determining whether a cell has a drug-resistant phenotype by measuring the expression (or activity) of DR6 in the cell and comparing this expression to that in a control cell. Increased expression (or activity) of DR6 in the cell compared to the Control cell indicates that the cell has a drug-resistant phenotype. In one embodiment of this method, DR6 expression is determined by measuring DR6 protein (e.g., measuring DR6 protein using an antibody directed against DR6). In another embodiment, DR6 expression is measured by quantifying mRNA encoding DR6 or the copy number of the DR6 gene. In another embodiment DR6 activity is measured using any assay which can quantify a biological activity of DR6.
The invention also includes a method for modulating the drug resistance of a cell by modulating DR6 expression or activity within the cell. Thus in one embodiment, the drug-resistance of a cell is reduced by contacting the cell with a molecule (e.g., an antisense nucleic acid molecule) that reduces the expression of DR6 within the cell.
Another aspect of the present invention is a method of improving effectiveness of chemotherapy for a mammal having a disorder associated with the presence of drug-resistant neoplastic cells. In this method, a chemotherapeutic drug and a molecule that reduces expression of DR6 can be co-administered to a mammal.
The invention also includes a method of identifying a compound that modulates the drug resistance of a cell by first contacting the cell with a test compound and then measuring and comparing DR6 expression in the cell exposed to the compound to DR6 expression in a control cell not exposed to the compound. The compound is identified as modulator of drug resistance when the level of DR6 expression in the cell exposed to the compound differs from the level of DR6 expression in cells not exposed to the compound. In one embodiment of this method, the cell has a drug-resistant phenotype. In another embodiment, the cell is a mammalian cell. This method may also include an optional step of measuring the drug resistance of the cell in the presence of the identified modulator of drug resistance. The DR6 modulating compounds that are identified in the foregoing methods are also included within the invention.
The invention also features a method of treating a mammal suspected of having a disorder associated with the presence of drug-resistant cells. This method includes the steps of determining whether a mammal has a disorder associated with the presence of drug-resistant cells having increased DR6 expression (e.g., drug-resistant cancer), and administering to the mammal a compound that sufficiently reduces the expression of DR6 so that the drug resistance of the cells associated with the disorder is modulated (i.e., reduced).
Another feature of the invention is a method for treating a patient having a neoplastic disorder (e.g., cancer) by administering to the patient a therapeutically effective amount of a compound that decreases the expression of DR6.
In the context of cancer treatment, the expression level of DR6 may be used to: 1) determine if a cancer, particularly a drug resistant cancer, can be treated by an agent or combination of agents; 2) determine if a cancer is responding to treatment with an agent or combination of agents; 3) select an appropriate agent or combination of agents for treating a cancer; 4) monitor the effectiveness of an ongoing treatment; and 5) identify new cancer treatments (either single agent or combination of agents). In particular, DR6 may be used as a marker (surrogate and/or direct) to determine appropriate therapy, to monitor clinical therapy and human trials of a drug being tested for efficacy and in developing new agents and therapeutic combinations.
Accordingly, the present invention provides methods for determining whether an agent, e.g., a chemotherapeutic agent such as doxorubicin or vinblastine, will be effective in reducing the growth rate of cancer cells comprising the steps of: a) obtaining a sample of cancer cells; b) determining the level of expression in the cancer cells of DR6; and c) identifying that an agent will be effective when DR6 is not expressed or is expressed at relatively low level. Alternatively, in step (c), an agent can be identified as being relatively ineffective when to use to treat the cancer when DR6 is expressed or is expressed at relatively high level.
As used herein, an agent is said to reduce the rate of growth of cancer cells when the agent can reduce at least 50%, preferably at least 75%, most preferably at least 95% of the growth of the cancer cells. Such inhibition can further include a reduction in survivability and an increase in the rate of death of the cancer cells. The amount of agent used for this determination will vary based on the agent selected. Typically, the amount will be a predefined therapeutic amount.
As used herein, an agent is defined broadly as anything that cancer cells can be exposed to in a therapeutic protocol. In the context of the present invention, such agents include, but are not limited to, chemotherapeutic agents, such as anti-metabolic agents, e.g., Ara AC, 5-FU and methotrexate, antimitotic agents, e.g., Taxol, vinblastin and vincristine, alkylating agents, e.g., melphanlan, BCNU and nitrogen mustard, Topoisomerase II inhibitors, e.g., VW-26, topotecan and Bleomycin, strand-breaking agents, e.g., doxorubicin and DHAD, cross-linking agents, e.g., cisplatin and CBDCA, radiation and ultraviolet light. Preferred agents are doxorubicin and vinblastine.
The agents tested in the present methods can be a single agent or a combination of agents. For example, the present methods can be used to determine whether a single chemotherapeutic agent, such as methotrexate, can be used to treat a cancer or whether a combination of two or more agents can be used.
Cancer cells include, but are not limited to, carcinomas, such as squamous cell carcinoma, basal cell acarcinoma, sweat gland carcinoma, sebaceous gland carcinoma, adenocarcinoma, papillary carcinoma, papillary adenocarcinoma, cystadenocarcinoma, medullary carcinoma, undifferentiated carcinoma, bronchogenic carcinoma, melanoma, renal cell carcinoma, hepatoma-liver cell carcinoma, bile duct carcinoma, cholangiocarcinoma, papillary carcinoma, transitional cell carcinoma, choriocarcinoma, semonoma, embryonal carcinoma, mammary carcinomas, gastrointestinal carcinoma, colonic carcinomas, bladder carcinoma, prostate carcinoma, and squamous cell carcinoma of the neck and head region; sarcomas, such as fibrosarcoma, myxosarcoma, liposarcoma, chondrosarcoma, osteogenic sarcoma, chordosarcoma, angiosarcoma, endotheliosarcoma, lymphangiosarcoma, synoviosarcoma and mesotheliosarcoma; leukemias and lymphomas such as granulocytic leukemia, monocytic leukemia, lymphocytic leukemia, malignant lymphoma, plasmocytoma, reticulum cell sarcoma, or Hodgkins disease; and tumors of the nervous system including glioma, meningoma, medulloblastoma, schwannoma or epidymoma.
The source of the cancer cells used in the methods of the invention will be based on how the method of the present invention is being used. For example, if the method is being used to determine whether a patient""s cancer can be treated with an agent, or a combination of agents, then the preferred source of cancer cells will be cancer cells obtained from a cancer biopsy from the patient. Alternatively, cancer cells line of similar type to that being treated can be assayed. For example if breast cancer is being treated, then a breast cancer cell line can be used. If the method is being used to monitor the effectiveness of a therapeutic protocol, then a tissue sample from the patient being treated is the preferred source. If the method is being used to identify new therapeutic agents or combinations, then any cancer cells, e.g., cells of a cancer cell line, can be used.
A skilled artisan can readily select and obtain the appropriate cancer cells that are used in the present method. For cancer cell lines, sources such as The National Cancer Institute, for the NCI-60 cells used in the examples, are preferred. For cancer cells obtained from a patient, standard biopsy methods, such as a needle biopsy, can be employed.
In the methods of the present invention, the level or amount of expression of DR6 is determined. As used herein, the level or amount of expression refers to the absolute level of expression of an mRNA encoded by the gene or the absolute level of expression of the protein encoded by the gene (i.e., whether or not expression is or is not occurring in the cancer cells).
As an alternative to making determinations based on the absolute expression level of selected genes, determinations may be based on the normalized expression levels. Expression levels are normalized by correcting the absolute expression level of a sensitivity or resistance gene by comparing its expression to the expression of a gene that is not a sensitivity or resistance gene, e.g., a housekeeping genes that is constitutively expressed. Suitable genes for normalization include housekeeping genes such as the actin gene. This normalization allows one to compare the expression level in one sample, e.g., a patient sample, to another sample, e.g., a non-cancer sample, or between samples from different sources. Alternatively, the expression level can be provided as a relative expression level. To determine a relative expression level of a gene, the level of expression of the gene is determined for 10 or more samples, preferably 50 or more samples, prior to the determination of the expression level for the sample in question. The mean expression level of each of the gene assayed in the larger number of samples is determined and this is used as a baseline expression level for the gene in question. The expression level of the gene determined for the test sample (absolute level of expression) is then divided by the mean expression value obtained for that gene.
This provides a relative expression level and aids in identifying extreme cases of sensitivity or resistance.
Preferably, the samples used will be from similar tumors or from non-cancerous cells of the same tissue origin as the tumor in question. The choice of the cell source is dependent on the use of the relative expression level data. For example, using tumors of similar types for obtaining a mean expression score allows for the identification of extreme cases of sensitivity or resistance. Using expression found in normal tissues as a mean expression score aids in validating whether the gene assayed is tumor specific (versus normal cells).
Also within the invention is a method for increasing drug resistance in a cell having an undesirably low level of DR6 expression by administering a compound that increases the expression of DR6. Such methods are useful for the protection of non-neoplastic cells during chemotherapy.
The invention features a method for determining whether a test compound modulates the drug resistance of a cell, the method including: a) determining the level of DR6 expression (e.g., DR6 encoded by an endogenous or heterologous gene) in a cell in the presence of a test compound; b) determining the level of DR6 expression in the cell in the absence of the test compound; and c) identifying the compound as a modulator of drug resistance of the cell if the level of expression of DR6 in the cell in the presence of the best compound differs from the level of expression of DR6 in the cell in the absence of the test compound.
The invention also features a method for determining whether a test compound modulates the drug resistance of a cell, the method including: a) incubating DR6 protein in the presence of a test compound; b) determining whether the test compound binds to the DR6 protein; c) selecting a test compound which binds to the DR6 protein; d) administering the test compound selected in step c) to a non-human mammal having drug resistant cells; e) determining whether the test compound alters the drug resistance of the cells in the non-human mammal; and f) identifying the test compound as a modulator of drug resistance of the cell if the compound alters the drug resistance of the cells in step e).
The invention further features a method for determining whether a test cell has a drug-resistant phenotype, the method including: a) measuring the expression of DR6 in the test cell; b) comparing the expression of DR6 measured in step a) to the expression of DR6 in a control cell not having a drug-resistant phenotype; and c) determining that the test cell has a drug resistant phenotype if the expression of DR6 in the test cell is greater than the expression of DR6 in the control cell.
In another aspect the invention features a method of determining whether a test cell has a drug-resistant phenotype, the method including: a) measuring the activity of DR6 in the test cell; b) comparing the activity of DR6 measured in step a) to the activity of DR6 in a control cell not having a drug-resistant phenotype; and c) determining that the test cell has a drug resistant phenotype if the activity of DR6 in the test cell is greater than the activity of DR6 in the control cell.
In yet another aspect the invention features a method for determining whether a subject has or is at risk of developing a drug resistant tumor, the method including: a) measuring the expression of DR6 mRNA in a biological sample obtained from the subject (using, e.g., a nucleic acid molecule that hybridizes to DR6 mRNA); b) comparing the expression of DR6 mRNA measured in step a) to the expression of DR6 mRNA in a biological sample obtained from a control subject not having a drug resistant tumor; and c) determining that the patient has or is at risk of developing a drug resistant tumor if the expression of DR6 mRNA in the biological sample obtained from the patient is higher than the expression of DR6 mRNA in the biological sample obtained from the control subject.
In still another aspect the invention features a method for determining whether a subject has or is at risk of developing a drug resistant tumor, the method including: a) measuring the activity of DR6 in a biological sample obtained from the subject (using, e.g., an agent that binds to DR6 protein); b) comparing the activity of DR6 measured in step a) to the expression of DR6 mRNA in a biological sample obtained from a control subject not having a drug resistant tumor; and c) determining that the patient has or is at risk of developing a drug resistant tumor if the activity of DR6 in the biological sample obtained from the patient is higher than the activity of DR6 in the biological sample obtained from the control subject.
The invention also features a method for monitoring the effect of an anti-tumor treatment on a patient, the method including: a) measuring the expression of DR6 in a tumor sample obtained from the patient (using, e.g., a nucleic acid molecule that hybridizes to DR6 mRNA); b) comparing the expression of DR6 measured in step a) to the expression of DR6 in a control sample of cells; and c) determining that the anti-tumor treatment should be discontinued or modified if the expression of DR6 in the tumor sample is higher than the expression of DR6 in the control sample of cells.
The invention also features a method for monitoring the effect of an anti-tumor treatment on a patient, the method including: a) measuring the activity of DR6 in a tumor sample obtained from the patient (using, e.g., an agent that binds to DR6 protein); b) comparing the activity of DR6 measured in step a) to the activity of DR6 in a control sample of cells; and c) determining that the anti-tumor treatment should be discontinued or modified if the activity of DR6 in the tumor sample is higher than the activity of DR6 in the control sample of cells.
The invention further features a method for modulating the drug resistance of a cell by modulating DR6 expression within the cell and a method for reducing the drug resistance of cell by contacting the cell with a molecule which reduces the expression of DR6 within the cell.
The invention also features a method of increasing the effectiveness of a chemotherapeutic compound in a patient suffering from a disorder associated with the presence of drug-resistant neoplastic cells, the method including: a) administering a chemotherapeutic compound to the patient; and b) administering a compound with reduces DR6 expression to the patient.
The invention features a method of treating a mammal suspected of having a disorder associated with the presence of drug-resistant cells, the method including administering to the mammal a compound that reduces the expression of DR6 in the drug-resistant cells, the reduction be sufficient to reduce the drug resistance of the drug resistant cells and a method for increasing the drug resistance of cell that has an undesirably low level of DR6 expression, the method including exposing the cell to a compound that increases the expression of DR6.
The invention also features a method for treating a drug resistant tumor in a patient, the method comprising administering to said subject an amount of a MDA-9 antagonist effective to reduce drug resistance of said tumor in the patient. In another aspect, the invention features the use of an inhibitor of MDA-9 expression, or pharmaceutically acceptable salt thereof, or a pharmaceutical composition containing either entity, for the manufacture of a medicament for the treatment of a drug resistant tumor in a patient.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one or ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In addition, the materials, methods, and examples are illustrative only and are not intended to be limited. Other features and advantages of the invention will be apparent from the detailed description and from the claims.